The muffler with tailpipe is still available, try Stevinson with our club discount. SOR is listing them for only $120, not much more than a quality aftermarket unit. The down pipe and mid pipe are discontinued, so it looks like you'll need a muffler shop to bend you up new ones. I recently tried out a new place in Evergreen that made up a new tail pipe for my 1978 FJ45 for about $80, they did it while I waited in about an hour. Name of the place is Evergreen Auto Works, 30746 Bryant Dr. #312 Evergreen, CO 80439 303-674-7706.
A lot of the hanger hardware is still available new, I recently purchased all new hardware for my 1976 FJ40 from Stevinson.
The problem for this vintage (assuming your 1978) is if you need a new down pipe. Factory is double wall. You may be able to get a single wall down pipe made up, and they can cut off your old flanges and weld them up to the new pipe. What condition are your down pipe and mid pipes? My down pipe wasn't too bad, so I sand blasted it and painted it with silver exhaust paint (1400°F rating).